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An isotope of Thorium had an initial activity of 112 \mathrm{dpm}. After 69.3 \mathrm{~min},it was found to have an activity of 56 \mathrm{dpm}

Find the number of atoms in a sample having activity of 100 \mathrm{dpm}:

Option: 1

10


Option: 2

1000


Option: 3

56


Option: 4

10000


Answers (1)

best_answer

\mathrm{\lambda=\frac{0.693}{69.3}=10^{-2} \mathrm{~min}^{-1} }

\mathrm{\left\{112 \mathrm{dpm} \rightarrow 56 \mathrm{dpm}, t_{1 / 2}=69.3 \mathrm{~min}\right\}}

\mathrm{N=\frac{-\frac{d N}{d t}}{\lambda}=\frac{100}{10^{-2}}=10000}

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shivangi.shekhar

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